A method of providing a concentrate of a dissolved substance for producing a dialysis solution includes providing a container containing a solid to be dissolved, supplying water into the container for dissolving the solid, draining the concentrate of the dissolved substance from the container and topping up with water, measuring the concentration of the dissolved substance or of a parameter correlated with the concentration, and temporary or permanent suppression of the topping up of water into the container. The suppression is effected when the measured concentration value of the dissolved substance falls below a first limit value or the value of the parameter falls below or exceeds a first limit value or when the change in the concentration value of the dissolved substance or of the value of the parameter exceeds a first limit value.